Legal pope during the Western Schism; born at Venice, of a noble family, about 1327; died at Recanati, 18 October, 1417.

He became Bishop of Castello in 1380 and titular Patriarch of Constantinople in 1390. Under Pope Innocent VII he was made Apostolic secretary, the Legate of Ancona, and finally, in 1405, Cardinal-Priest of San Mareo. It was due to his great piety and his earnest desire for the end of the schism that after the death of Innocent VII the cardinals at Rome unanimously elected him pope on 30 Nov., 1406. He took the name of Gregory XII. Before the papal election each cardinal swore that in order to end the schism he would abdicate the papacy if he should be elected, provided his rival at Avignon (Benedict XIII) would do the same. Gregory XII repeated his oath after his election and to all appearances had the intention to keep it. On 12 Dec., 1406, he notified Benedict XIII of his election and the stipulation under which it took place, at the same time reiterating his willingness to lay down the tiara if Benedict would do the same. Benedict apparently agreed to the proposals of Gregory XII and expressed his desire to have a conference with him. After long negotiations the two pontiffs agreed to meet at Savona. The meeting, however, never took place. Benedict, though openly protesting his desire to meet Gregory XII, gave various indications that he had not the least intention to renounce his claims to the papacy; and Gregory XII, though sincere in the beginning, also soon began to waver. The relatives of Gregory XII, to whom he was always inordinately attached, and King Ladislaus of Naples, for political reasons used all their efforts to prevent the meeting of the pontiffs. The reason, pretended or real, put forth by Gregory XII for refusing to meet his rival, was his fear that Benedict had hostile designs upon him and would use their conference only as a ruse to capture him. The cardinals of Gregory XII openly showed their dissatisfaction at his procedure and gave signs of their intention to forsake him. On 4 May, 1408, Gregory XII convened his cardinals at Lucca, ordered them not to leave the city under any pretext, and created four of his nephews cardinals, despite his promise in the conclave that he would create no new cardinals. Seven of the cardinals secretly left Lucca and negotiated with the cardinals of Benedict concerning the convocation of a general council by them at which both pontiffs should be deposed and a new one elected. They summoned the council to Pisa and invited both pontiffs to be present. Neither Gregory XII nor Benedict XIII appeared. At the fifteenth session (5 June, 1409), the council deposed the two pontiffs, and elected Alexander V on 26 June, 1409. Meanwhile Gregory stayed with his loyal and powerful protector, Prince Charles of Malatesta, who had come to Pisa in person during the process of the council, in order to effect an understanding between Gregory XII and the cardinals of both obediences. All his efforts were useless. Gregory XII, who had meanwhile created ten other cardinals, convoked a council at Cividale del Friuli, near Aquileia, for 6 June, 1409. At this council, though only a few bishops had appeared, Benedict XIII and Alexander V were pronounced schismatics, perjurers, and devastators of the Church.

Though forsaken by most of his cardinals, Gregory XII was still the true pope and was recognized as such by Rupert, King of the Romans, King Ladislaus of Naples, and some Italian princes. The Council of Constance finally put an end to the intolerable situation of the Church. At the fourteenth session (4 July, 1415) a Bull of Gregory XII was read which appointed Malatesta and Cardinal Dominici of Ragusa as his proxies at the council. The cardinal then read a mandatory of Gregory XII which convoked the council and authorized its succeeding acts. Hereupon Malatesta, acting in the name of Gregory XII, pronounced the resignation of the papacy by Gregory XII and handed a written copy of the resignation to the assembly. The cardinals accepted the resignation, retained all the cardinals that had been created by him, and appointed him Bishop of Porto and perpetual legate at Ancona. Two years later, before the election of the new pope, Martin V, Gregory XII died in the odour of sanctity.